Instrumentation of Steel Sheet Pile Wall and Steep Cut

Slopes in Piedmont Residual Soils for Research

Michael Valiquette – ICE of Carolinas

Jungmok Lee – Subsurface Construction

Roy Borden – North Carolina State University

Mohammed Gabr – North Carolina State University

April 11, 2017

Location of Test Site

Test Site

Test Site Plan View

Test Site Cross-Section

Test Site Overhead Photo

Test Slopes

Test Wall

Subsurface Condtions

Additional Subsurface Investigation

Additional Subsurface Investigations

CPT, DMT, SPTPressuremeterTriaxialConsolidation

Test Slope 1 Test Slope 2 Test Slope 3

Additional Subsurface Investigations

Soil Suction Measurements

Sheet Piling, PZC-13

Strain Gauge Installation

Strain Gauge Installation

Strain Gauge Cover Angles

Strain Gauge Cover Angles

Sheet Pile Vibratory Refusal,

Advanced to tip with Diesel Hammer

Push in Pressure Cells

Push in Pressure Cells

In situ Instrumentation

In situ Instrumentation

In situ Instrumentation, Moisture Sensor

In situ Instrumentation, Suction Sensors

In situ Instrumentation, Suction Sensors

In situ Instrumentation, Suction Sensors

Initial Excavation Stage

Initial Excavation Stage

LiDAR Scanning

LiDAR Scanning

Infiltration Ponds

Full Height Excavation

Full Height Excavation

Full Height Excavation

Picture of field site after 6.7 m excavation

Excavation depths over time

Classification of test site soils

Soil 1 Soil 2

Gs 2.75 2.74

LL 35 58

PI 7 21

% of fine content 58 88

AASHTO A-4 A-7-5

USCS ML MHBy Wang (2014)

Effective strength parameter (By Tang, 2014)

• A-7-5 soil : φ’= 27° and c’=10 kPa• A-4 soil : φ’= 30° without effective cohesion

Saturated permeability (Ks)

•A-7-5 soil : 3.15 x 10^-5 cm/s•A-4 soil : 5.9 x 10^-5 cm/s

Location of instruments at sheet pile wall area

Soil characteristic profiles (BH 2)

Cross-section of test site

BH3 BH2

Initial suction profiles

BH 3 BH 2 BH 1

Field SWCC for sheet pile wall area

0

0.1

0.2

0.3

0.4

0.5

0.6

0.1 1 10 100 1000 10000 100000 1000000

Vo

lum

etr

ic W

ate

r C

on

ten

t, θ

matric suction (kPa)

Suction by pressure platetests

Suction by tensiometer

Sample

Location

Depth

(m)

Soil

type

a

(1/kPa)n m

BH2

4.5 A-4 0.435 0.038 0.034 1.771 0.435

10.4 A-4 0.509 0.038 0.050 1.589 0.371

13.5 A-4 0.490 0.038 0.065 1.511 0.338

BH31.6 A-7-5 0.533 0.17 0.078 1.328 0.247

13.5 A-4 0.456 0.038 0.057 1.678 0.404

s r

Wang (2014)

Measured displacement of soil

Observed gap and cracks

after 6.1 m excavation after 6.7 m excavation

Suction profile (BH 2) from FTC

Movement of sheet pile wall

Bending moments obtained from

measured strain gauge

4.6 m excavation 6.1 m excavation 6.7 m excavation

4.6 m6.1 m 6.7 m

Measured lateral stress change using

pressure cell

FEM Modeling of Wall

Field tests for the slopes

Geometry of model for 0.25:1 slope

0.25 :1 6.7 m

Material properties for 0.25:1 slope

Initial suction profile

0.25 :1 0.5 :1 1 :1

FS for different initial matric suction

profile

Initial matric suction

profile

FS

0.25:1 slope 0.5:1 slope 1:1 slope

Measured 1.55 1.75 1.91

No matric suction 0.80 1.02 0.86

Lateral displacement from inclinometer

Conclusion

• Measurement of Instrumentations help us understand the behavior of unsaturated Piedmont Residual soils

• NCDOT determining how to incorporate research results into construction practices

REFERENCE

• Wang, Cheng. (2014). Soil Suction Characterization and New Model for Predicting Suction in Residual Soil. North Carolina State University, Raleigh, NC

• Tang, Chien-ting. (2016). Predication of Shear Strength as a Function of Matric Suction for North Carolina Residual Soils. North Carolina State University , Raleigh, NC

• Lee, Jungmok. (2016). Analysis and Design of Temporary Slopes and Excavation Support Systems in Unsaturated Piedmont Residual Soils. North Carolina State University , Raleigh, NC

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Questions ?